Answer:
9
Explanation:
For the equation to have more than one solution, that is infinite solutions, then both sides should be equal.
left side is
5u + 3(4u - 6)
= 5u + 12u - 18 = 17u - 18
right side is
- 3u - 27 + 20u
= 17u - 27 ← require to add 9 so equal to left side, that is
17u - 27 + 9
= 17u - 18